Plastid

PLASTID

Nature and Occurrence:

Several small coloured bodies found in the cytoplasm of plant cells, scattered in the cytoplasm of the leaf cells. These are called plastids.
They are of different colours.

Structure:

They are oval or cylindrical in shape.
They are double membrane structure, consisting of outer and inner membrane.
Outer membrane is smooth/ flat and inner membrane is folded into many layers internally.
Each fold is known as thyllakoid.
These thyllakoids are arranged in the form of stacks called grana.
The lumen of plastid is filled with jelly like substance called as stroma.
This stroma contains water and other biochemicals like carbohydrates, proteins, amino acids, lipids etc.
Just like mitochondria, plastids also contains their own DNA.
The thyllakoids contains some coloured pigments which imparts colour to the organ where it is present.

On the basis of presence of these coloured pigments plastids are of two types: chromoplast and leucoplast.

Chromoplast are coloured due to presence of coloured pigments.
Chloroplast appears green in colour due to presence of green pigment called chlorophyll.

Leucoplast is colourless and is meant for storage of different substances like sugars (amyloplast), lipids (elaioplast), protein (proteinoplast) etc in plants.

Provide to colour to different parts of the plants:

Chromoplast imparts colour to the different parts of the plants like leaves, flowers vegetables, fruits etc.

Pollination:

Coloured flowers help in the process of cross pollination by attracting the insects towards themselves. When insects sits over these flowers will pick the pollen grains and transfer them to the other flowers thus helping in cross pollination to occur.

Photosynthesis:

Chloroplasts are found in green parts of the plants and are essential for photosynthesis.

Storage of different components:

Leucoplast helps in storage of different components of the cell like lipids, carbohydrates and proteins.